I think I have had a relevation, but can someone correct me if I'm wrong. Since vk is an element of S, and because S spans V, T cannot span V because it does not span S. And since every vector in V can be written as a linear combination of S, every vector of V can not be written as a linear combination of T.
Is explaining this enough to justify my conclusion? I can't think of a more numerical way to show this.